Heat distribution structure, manufacturing method for the same and heat-dissipation module incorporating the same

ABSTRACT

A heat distribution structure, a method for manufacturing the same and a heat-dissipation module incorporating the same are disclosed. The heat distribution structure includes a first cap with a first grove and a second cap with a second groove and a support body interposed between the first cap and the second cap, wherein microstructures are formed at the bottoms of the first groove and the second groove and through holes are formed in the support body. The support body is interposed between the first and second caps, such that a cavity is formed by the first cap, the support body and the second cap. A working fluid is contained in the cavity that flows therein through capillary action provided by the microstructures of the first and second grooves and the through holes in the support body, thus evenly distributing heat in the heat distribution structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to heat distribution structures,manufacturing methods for the same and heat-dissipation modulesincorporating the same, and, more particularly, to a heat distributionstructure that enhances the effect of heat distribution, a manufacturingmethod for the same and heat-dissipation module incorporating the same.

2. Description of Related Art

Light emitting diodes (LED) typically have the advantages of low powerconsumption, fast response speed, and small volume and have become amain alternative to conventional incandescent or fluorescent bulbs.However, the LEDs convert about half of its input power into heat duringlight emission. Although such heat is in the level of only a few watts,due to small volumes of the LEDs, heat density is relatively high andleading to hot spots with extremely high temperature at die attachmentarea. This reduces the efficiency of the LEDs and/or shortens theservice life of the LEDs.

To prevent overheating of the LED dies, an LED is disposed on a heatdissipating substrate in the prior art, such as a copper foil printedcircuit board, a metal-based printed circuit board or a ceramicsubstrate. However, the heat transfer coefficient of a copper foilprinted circuit board is approximately 0.36 W/mk. This indicates poorheat transfer and causes overheating of the LED. FIG. 1 is a schematicdiagram illustrating the use of a metal-based printed circuit board. Ina heat-dissipating module 1, an LED 11 is fixed to a substrate 13 via anadhesive 12, and the substrate 13 is disposed on a heat-dissipatingsubstrate including a dielectric layer 14 and a metal layer 15, and theheat-dissipating substrate is then attached to a heat-dissipatingstructure 17 via a thermal interface material (TIM) 16.

In FIG. 1, heat (as indicated by arrows) generated by the LED 11 ispropagated sequentially through the substrate 13, the dielectric layer14 and the metal layer 15 to the heat-dissipating structure 17. In thispropagation path, heat is met with at least three layers of dissipatingresistances. In addition, the dielectric layer 14 has difficulty ofevenly distributing spot heat source generated at the attachmentlocation of the LED 11 to the plane of the metal layer 15. Moreover, thedielectric layer is usually made of epoxy resin with poor thermalconductivity, so that it often becomes a heat-dissipating bottleneck forthe heat-dissipating module, and renders the overall heat transfercoefficient to be only 1 to 12 W/mk. In addition, relevant art alsoproposes using a ceramic substrate as the heat-dissipating substrate.Although it has relatively better dielectric characteristics and lowerthermal expansion coefficient, and a good heat transfer performance(with a heat transfer coefficient of about 170 W/mk), but ceramicsubstrates did not address the “hot spot” issue faced by currenthigh-power LEDs. Alternatively, even if materials of high thermalconductivities such as diamond like carbon films are used, which haveheat transfer coefficients as high as between 200 to 600 W/mk in thehorizontal direction, and heat transfer coefficients lower than 10 W/mkin the vertical direction, they are still not sufficient in overcomingthe “hot spot” problem faced by the current high-power LEDs.

U.S. Pat. Nos. 6,274,924, 6,943,433, 7,361,490 and 7,208,772 and U.S.Patent Publication Nos. 2006/0086945 and 2005/0269587 mainly focus onthe design of incorporating heat-dissipating blocks in packagestructures, but their heat transfer characteristics are all limited bythe heat transfer characteristics of the metal materials used for theheat-dissipating blocks. Furthermore, U.S. Pat. Nos. 6,717,246 and6,789,610 as well as U.S. Patent Publication No. 2006/0243425 disclosethe use of a flat plate heat pipe, which allows heat transfer throughthe phase change of a working fluid inside the pipe. Using two-phasechange and flowing of the working fluid for heat transfer, heat spreadis better than metal plate of the same size, and temperaturedistribution is more even. However, existing flat plate heat pipe isusually made of copper, which can be challenging in terms of integrationin the die manufacturing process.

SUMMARY OF THE INVENTION

The present invention provides a heat distribution structure, whichcomprises a first cap formed with a first groove, a second cap formedwith a second groove, a plurality of microstructures formed at bottomsof the first groove and the second groove, a support body formed with aplurality of through holes interposed between the first cap and thesecond cap, wherein the first groove and the second groove face thesupport body, such that a cavity is formed by the first cap, the supportbody and the second cap, and a working fluid accommodated in the cavitythat flows within the cavity via the plurality of microstructures andthe plurality of through holes.

A heat-dissipation module for dissipating heat generated by a dieaccording to an embodiment of this disclosure can be formed by combiningthe heat distribution structure of this disclosure and aheat-dissipation structure by a thermal interface material. Theheat-dissipation module includes: a heat-dissipation structure; thethermal interface material applied onto the heat-dissipation structure;the heat distribution structure proposed by this disclosure provided onthe heat-dissipation structure with the thermal interface materialinterposed therebetween, wherein an insulating layer is provided on asurface of the heat distribution structure away from the thermalinterface material; a metal layer formed on the insulating layer of theheat distribution structure; and the die provided on the metal layer.

A method for manufacturing a heat distribution structure according to anembodiment of this disclosure includes the following steps: (1) forminga plurality of microstructures at bottoms of a first groove of a firstcap and a second groove of a second cap, forming a guiding hole on thefirst cap or the second cap, and forming a plurality of through holes ina support body; (2) interposing the support body between the first capand the second cap in a manner of the first groove and the second groovefacing the support body so as to form a cavity between the first cap,the support body and the second cap; and (3) introducing a working fluidinto the cavity via the guiding hole, and then sealing the guiding hole,such that the working fluid flows within the cavity via themicrostructures and the through holes.

Compared with the prior art, the heat distribution structure of thisdisclosure and the manufacturing method for the same allow heat to beevenly distributed by allowing the working fluid to flow within thecavity of the heat distribution structure through capillary actioncaused by the plurality of microstructures and through holes, solvingthe “hot spot” problem. Moreover, the heat-dissipation moduleincorporating the heat distribution structure of this disclosureeliminates the multiple dissipating resistances in the traditionalheat-dissipation modules, improving efficiency of heat dissipation ofthe heat-dissipation module, which in turn stabilizes the performance ofthe LEDs.

BRIEF DESCRIPTION OF THE DRAWINGS

This disclosure can be more fully understood by reading the followingdetailed description of the preferred embodiments, with reference madeto the accompanying drawings, wherein:

FIG. 1 is a schematic diagram illustrating a conventionalheat-dissipation module;

FIG. 2 is a schematic diagram illustrating a heat distribution structureof this disclosure;

FIG. 3 is a flowchart illustrating a method for manufacturing a heatdistribution structure of this disclosure;

FIG. 4 is a schematic diagram illustrating a heat-dissipation moduleincorporating a heat distribution structure of this disclosure; and

FIGS. 5A and 5B are graphs depicting test results of the temperatures ofa conventional heat-dissipation module and the heat-dissipation moduleaccording to this disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

This disclosure is described by the following specific embodiments.Those with ordinary skills in the arts can readily understand the otheradvantages and functions of this disclosure after reading the disclosureof this specification. This disclosure can also be applied orimplemented in different embodiments.

In light of the drawbacks in the art, embodiments according to thisdisclosure provide a heat distribution structure, a manufacturing methodfor the same and a heat-dissipation module incorporating the same thatachieve good and even heat distribution, which increases the performanceof a die provided in the heat-dissipation module. It should be notedthat the structures, proportions, sizes and the like shown in thedrawings of this disclosure are only to accompany the contents disclosedin this specification and to facilitate understanding and reading bythose with ordinary skill in the art. They are not to limit theconditions in which this disclosure can be embodied, so they have notechnical substantial meanings. Any modifications to the structures,proportions, sizes and the like are construed as falling within thescope of this disclosure so long as they do not affect the effectsgenerated and the objectives achieved by this disclosure. Similarly,terms such as “above”, “below”, “first” and “second” cited in thisspecification are to facilitate understanding of the descriptions andare not used to limit the scope of this disclosure. Any modifications orchanges in relative relationships are construed to be within the scopeof this disclosure so long as there is no substantial technical change.

A heat distribution structure, a manufacturing method for the same and aheat-dissipation module incorporating the same according to embodimentsof this disclosure are described in details below with reference to thedrawings.

Referring to FIG. 2, a cross-sectional diagram illustrating a heatdistribution structure of this disclosure is shown. The heat structure20 includes a first cap 21, a support body 22, a second cap 23 and aworking fluid 25.

The first cap 21 includes a first groove 210, wherein a plurality ofmicrostructures 211 a are formed at the bottom 211 of the first groove210. The second cap 23 has a second groove 230, wherein a plurality ofmicrostructures 231 a are formed at the bottom 231 of the second groove230. The microstructures 211 a and 231 a can be formed at the bottom 211of the first groove 210 and the bottom 231 of the second groove 230,respectively by etching or other techniques. As shown in FIG. 2,microstructures 211 a and 231 a can be protrusions protruded from thebottoms 211 and 231, respectively. It should be noted that the first cap21 and the second cap 23 are the same components in principle, and thedirections in which the plurality of microstructures 211 a and 231 aextend are substantially parallel to each other, but are not limited tobeing aligned to the same normal. In addition, the first cap 21 and thesecond cap 23 are made of silicon and fabricated by lithographyprocesses.

The support body 22 includes a plurality of through holes 220. Thethrough holes 220 can be formed in the support body 22 by laser or othertechniques, wherein the directions in which the plurality of throughholes 220 extend are substantially parallel to each other. The supportbody 22 is interposed between the first cap 21 and the second cap 23,and the first groove 210 of the first cap 21 and the second groove 230of the second cap 23 face each other with the support body 22 interposedtherebetween. The first cap 21, the second cap 23 and the support body22 can be formed into an integrated structure using a high-temperatureand high pressure anode manufacturing process. In addition, as shown inFIG. 2, the first cap 21 and the second cap 23 sandwich the support body22 between the first cap 21 and the second cap 23, allowing a cavity 24to be formed between the first cap 21, the support body 22 and thesecond cap 23. The cavity 24 approaches around 10⁻³ Ton of vacuum state.Moreover, the material of the support body 22 is glass or glass with 4%of Na₂O.

The working fluid 25 is contained within the cavity 24. The workingfluid 25 flows in the cavity 24 through the plurality of microstructures211 a and 231 a and the plurality of through holes 220. The workingfluid 25 is for example water. More specifically, a guiding hole (notshown) can be formed in the first cap 21 or the second cap 23 tointroduce the working fluid 25 into the cavity 24. After the workingfluid 25 is introduced into the cavity 24, the guiding hole is thensealed.

It should be noted that the directions in which the plurality ofmicrostructures 211 a and 231 a in the cavity 24 and the through holes220 extend are substantially parallel to each other, the working fluidexhibit capillary phenomenon in the cavity 24 by the microstructures 211a and 231 a and the through holes 220, so the working fluid 25 can flowwithin the cavity 24 due to capillary action caused by themicrostructures 211 a and 231 a and the through holes 220. It should benoted that there are no particular limit to the sizes of themicrostructures 211 a and 231 a and the through holes 220 and the volumeof the working fluid 25 guided into the cavity 24. As shown in FIG. 2,the volume of the working fluid 25 does not completely cover theplurality of microstructures 231 a. Moreover, the working fluid 25 mayflow within the cavity 24. Thus, when the heat structure 20 is flippedover, the working fluid 25 will then cover the plurality ofmicrostructures 211 a due to gravity.

In an embodiment, if the spot heat source generated by a die isunderneath the second cap 23 of FIG. 2, then heat may be distributed inthe following process: the working fluid 25 spreads the spot heat sourceout into a plane via capillary action at the plurality of themicrostructures 231 a, then the plurality of through holes 220 absorbthe working fluid 25 through capillary action to the plurality of themicrostructures 211 a, and then the plurality of microstructures 211 adistribute the working fluid 25 into the first groove 210, andthereafter the working fluid 25 descends back to the second groove 230,to thereby complete a circulation. During a circulation of the workingfluid 25 in the cavity 24, the working fluid 25 may change from theliquid phase to the gaseous phase when heated, and after flowing to theunheated side, it changes from the gaseous phase back to the liquidphase, thus achieving the effect of heat dissipation.

Moreover, the sidewalls 241 of the cavity 24 (including the sidewall ofthe first groove 210, the sidewall of the second groove 230 or thesidewalls of the first groove 210 and the second groove 230) may be alsoformed with a plurality of microstructures 212 and 232 for increasingthe capillary action in the cavity 24 and thus enhancing the flow of theworking fluid 25 in the cavity 24.

From FIG. 2 it can be understood that in the heat distribution structureof this disclosure, through the microstructures and the through holes inthe cavity, the working fluid in the cavity exhibit capillary action sothat heat in the heat distribution structure can be evenly distributed,eliminating the “hot spot” problem produced when a die is provided, andthus improving die performance. In addition, the heat distributionstructure made of silicon and glass facilitates the installation of thedie.

Referring to FIG. 3, a flowchart illustrating the method formanufacturing the heat distribution structure of this disclosure isshown. First, a support body, a first cap and a second cap are provided.The material of the first cap and the second cap can be silicon, forexample. The material of the support body can be glass or glass with 4%of Na₂O.

In step S31, a first groove is formed in the first cap and a secondgroove is formed in the second cap; a plurality of microstructures areformed at the bottoms of the first and second grooves; a guiding hole isformed in the first cap or the second cap; and a plurality of throughholes are formed in the support body. Next, proceed to step S32.

In detail, by a technique of etching, the first groove and the secondgroove are formed in the first cap and the second cap, respectively, andthe microstructures are formed at the bottoms of the first and secondgrooves. In addition, a guiding hole can be formed at an arbitrarylocation of the first cap or the second cap for letting in a workingfluid. Furthermore, the through holes are formed in the support body bylaser. It should be noted that the order in which the sub-step forforming the plurality of microstructures at the bottom of the firstgroove, the sub-step for forming the plurality of microstructures at thebottom of the second groove and the sub-step for forming the pluralityof through holes inside the support body are carried out has noparticularly limit.

In step S32, the support body is sandwiched between the first cap andthe second cap in such a way that the first groove and the second grooveface the support body, thereby forming a cavity between the first cap,the support body and the second cap. Next, proceed to step S33.

More particularly, the material of the first and the second caps aretypically silicon. The material of the support body is typically glassor glass with 4% of Na₂O. The glass and the silicon can be combinedtogether with high heat (e.g. around 300 to 500° C.) and high pressure(e.g. around 500 to 1000V). The 02 in the glass and the Si₄ ⁺ in thesilicon form SiO₂ and covalently bond together. The combined silicon andglass has a strength of about 20 to 50 MPa. The first cap and thesupport body, and the second cap and the support body can be combinedtogether in this manner. Moreover, the first cap and the second capusing silicon as the main material can be easily integrated into the diemanufacturing process. In addition, in the cavity formed after combiningthe first cap, the support body and the second cap, the directions inwhich the plurality of microstructures at the bottom of the firstgroove, the plurality of microstructures at the bottom of the secondgroove and the plurality of through holes in the support body extend aresubstantially parallel to each other.

In step S33, a fluid (e.g. water) is guided into the cavity via theguiding hole, and then the guiding hole is sealed, so that the fluidflows within the cavity owing to the plurality of microstructures andthe plurality of through holes. Before the guiding hole is sealed, thecavity is made to be in a vacuum state of around 10⁻³ Ton.

It is known from FIG. 3, through the method for manufacturing the heatdistribution structure of this disclosure, an enclosed cavity can beformed in the heat distribution structure, and the bottoms the firstgroove and the second groove constitute the cavity have the plurality ofmicrostructures, while the support body between the first groove and thesecond groove has the plurality of through holes, such that the workingfluid in the cavity can flow within the first groove, the second grooveand the through holes, thereby achieving even distribution of heat.

Referring to FIG. 4, a cross-sectional diagram illustrating aheat-dissipation module incorporating the heat distribution structure ofthis disclosure is shown. FIG. 4 shows the heat structure 20 of FIG. 3or the heat distribution structure manufactured according to the stepsshown in FIG. 3 is applied to a heat-dissipation module 3 carrying adie.

The heat-dissipation module 3 includes a die 31, a metal layer 32, aninsulating layer 33, a heat distribution structure 30, a thermalinterface material 34 and a heat-dissipation structure 35.

The heat-dissipation structure 35 can be a heat sink. The thermalinterface material (TIM) 34 is applied onto the heat-dissipationstructure 35, and the heat distribution structure 30 is disposed on theheat-dissipation structure 35 with the thermal interface material 34interposed therebetween. The thermal interface material 34 fills thebonding gap between the heat distribution structure 30 and theheat-dissipation structure 35, thus expanding the heat-dissipation areabetween the heat distribution structure 30 and the heat-dissipationstructure 35.

The heat distribution structure 30 has all the characteristics of theheat structure 20 shown in FIG. 2. Sidewalls 301 of a cavity 300 of theheat distribution structure 30 also have a plurality of microstructures301 a. In addition, an insulating layer 33 is provided on a face 302 ofthe heat distribution structure 30 away from the thermal interfacematerial 34. The insulating layer 33 is a layer of silicon dioxide.

The metal layer 32 is formed on the insulating layer 33 of the heatdistribution structure 30. More particularly, metal (e.g. copper) can beformed by sputtering, electroplating or other techniques on theinsulating layer 33 of the heat distribution structure 30 as a circuitlayer. The die 31 is provided on the metal layer 32. In the case of anLED used as the die, it can be attached to the metal layer 32 byeutectic alloys.

Therefore, in FIG. 4, the spot heat source generated by the die 31 canbe distributed into a plane heat source by the heat distributionstructure 30, and then the heat can be transferred through large areacontact with the thermal interface material 34 and the heat-dissipationstructure 35, and finally dissipated through the heat-dissipationstructure 35.

Now, as shown in FIGS. 5A and 5B, graphs depicting test results of thetemperatures of a conventional heat-dissipation module and theheat-dissipation module according to this disclosure are shown, in whichthe heat-dissipation module carrying an LED is compared with atraditional heat-dissipation module carrying an LED as shown in FIG. 1in the prior art.

Referring to FIGS. 5A and 5B, in the prior art heat from the die to theheat-dissipation structure must encounter at least three spreadingresistances (i.e. the substrate, the dielectric layer and the metallayer), whereas the heat-dissipation module of this disclosureencounters only the insulating layer and the heat-dissipation structure,thus greatly reducing dissipating resistance and increasing heattransfer efficiency. Moreover, epoxy resin is typically used as thedielectric layer in the prior art, which has poor heat conductivity suchthat hot spots generated by the die cannot be distributed evenly, thisresults in the temperature difference between the heat-dissipationstructure and the die of FIG. 5A being much greater than the temperaturedifference between the heat-dissipation structure and the die of FIG.5B, implying heat of the prior art still concentrates around the dieitself and the die attachment area. This generates hot spots and reducesthe service life and performance of the LED. Furthermore, thetemperature difference between the metal layer and the heat-dissipationstructure is also quite large, indicating that heat cannot beefficiently transferred to the heat-dissipation structure. On thecontrary, through the heat distribution structure of this disclosure,due to the phase change and circulations of the working fluid in theheat distribution structure, spot heat source generated by the die canbe distributed evenly, and thus efficiently transferred to theheat-dissipation structure.

In summary, the heat distribution structure of this disclosure and theheat distribution structure manufactured by the method for manufacturinga heat distribution structure of this disclosure have the ability ofdistributing heat evenly. The heat-dissipation module incorporating theheat distribution structure of this disclosure reduces heat resistance,eliminates hot spots and facilitates integration with the diemanufacturing process, which are not only suitable for LEDs forincreasing their performances, but for other spot heat sources,providing a better heat conductivity.

The above embodiments are only used to illustrate the principles of thisdisclosure, and they should not be construed as to limit this disclosurein any way. The above embodiments can be modified by those with ordinaryskill in the art without departing from the scope of this disclosure asdefined in the following appended claims.

What is claimed is:
 1. A heat distribution structure comprising: a firstcap formed with a first groove and a second cap formed with a secondgroove, and a plurality of microstructures formed at bottoms of thefirst groove and the second groove; a support body formed with aplurality of through holes interposed between the first cap and thesecond cap, wherein the first groove and the second groove face thesupport body, such that a cavity is formed by the first cap, the supportbody and the second cap; and a working fluid accommodated in the cavitythat flows within the cavity via the microstructures and the throughholes.
 2. The heat distribution structure of claim 1, wherein aplurality of microstructures are further formed on a sidewall of thefirst groove, a sidewall of the sealed groove, or the sidewalls of thefirst groove and the second groove.
 3. The heat distribution structureof claim 1, wherein the cavity is in a vacuum state.
 4. The heatdistribution structure of claim 1, wherein the first and the second capsare made of silicon material.
 5. The heat distribution structure ofclaim 1, wherein the support body is made of glass.
 6. The heatdistribution structure of claim 1, wherein the working fluid is water.7. The heat distribution structure of claim 1, wherein themicrostructures of the first groove and the second groove areprotrusions.
 8. The heat distribution structure of claim 1, wherein thefirst cap, the second cap and the support body are formed into anintegrated structure by a high-temperature and high-pressure anodizingprocess.
 9. A method for manufacturing a heat distribution structure,comprising the steps of: (1) forming a plurality of microstructures atbottoms of a first groove of a first cap and a second groove of a secondcap, forming a guiding hole on the first cap or the second cap, andforming a plurality of through holes in a support body; (2) interposingthe support body between the first cap and the second cap in a manner ofthe first groove and the second groove facing the support body, suchthat a cavity is formed between the first cap, the support body and thesecond cap; and (3) introducing a working fluid into the cavity via theguiding hole, and then sealing the guiding hole, such that the workingfluid flows within the cavity via the microstructures and the throughholes.
 10. The method for manufacturing a heat distribution structure ofclaim 9, wherein step (1) further comprises forming a plurality ofmicrostructures in a sidewall of the first groove, a sidewall of thesecond groove, or the sidewalls of the first groove and the secondgroove.
 11. The method for manufacturing a heat distribution structureof claim 9, wherein the forming of the microstructures at the bottoms ofthe first groove and the second groove is performed by etching.
 12. Themethod for manufacturing a heat distribution structure of claim 9,wherein the forming of the through holes in the support body isperformed by laser.
 13. The method for manufacturing a heat distributionstructure of claim 9, wherein the (2) further comprises combining thefirst cap and the second cap with the support body interposedtherebetween under high temperature and high pressure.
 14. The methodfor manufacturing a heat distribution structure of claim 9, wherein,before the sealing of the guiding hole in step (3), step (3) furthercomprises making the cavity in a vacuum state.
 15. The method formanufacturing a heat distribution structure of claim 9, wherein thefirst cap and the second cap are made of silicon material by alithography process.
 16. A heat-dissipation module for dissipating heatgenerated by a die, the heat-dissipation module comprising: aheat-dissipation structure; a thermal interface material applied ontothe heat-dissipation structure; a heat distribution structure providedon the heat-dissipation structure with the thermal interface materialinterposed therebetween, and an insulating layer provided on a surfaceof the heat distribution structure away from the thermal interfacematerial, wherein the heat distribution structure comprises: a first capformed with a first groove and a second cap formed with a second groove,and a plurality of microstructures formed at bottoms of the first grooveand the second groove; a support body formed with a plurality of throughholes interposed between the first cap and the second cap, wherein thefirst groove and the second groove face the support body, such that acavity is formed by the first cap, the support body and the second cap;and a working fluid accommodated in the cavity that flows within thecavity via the microstructures and the through holes; a metal layerformed on the insulating layer of the heat distribution structure; andthe die provided on the metal layer.
 17. The heat-dissipation module ofclaim 16, wherein the die is a light emitting diode die.
 18. Theheat-dissipation module of claim 16, wherein the insulating layer is asilicon dioxide layer.